Casting cleaning



United States Patent 3,205,105 CASTING CLEANING Thomas H. Oster,Dearhorn, Mich., assignor to Ford Motor Company, Dearborn, Mich., acorporation of Delaware N0 Drawing. Filed Mar. 11, 1963, Ser. No.264,022 11 Claims. (Cl. 156-18) This invention relates to the ironfounding art and is more particularly concerned with a process forrapidly and economically removing fins from ferrous castings. Theprocedure taught by this invention is particularly applicable to theremoval of internal fins which are shielded by the configuration of thecasting from the usual me.- chanical de-finning expedients.

In the preparation of cores and molds for the recpetron of molten metalin the manufacturing of ferrous castings, the joints between sections ofthe molds or cores are often imperfect. These imperfect joints permitmetal to flow in between the mold sections and result in the productionof thin metallic fins which are firmly attached to the remainder of thecasting. The removal of these fins from external portions of the castingis readily accomplished by ordinary mechanical means. However, thesefins are often located internally of a casting so that they are shieldedfrom mechanical removal. No satis factory means of dealing'with theseinternal fins has been found. This difiiculty is particularly apparentin complex castings suchas internal combustion enginge cylinder heads,although it is by no means limited to this structure. The fins occurringinternally in internal combustion cylinder heads often block orpartially block cooling waterpassages with the result that hot spots andwarpage are inevitable when the engine is operated.

Accordingly, it is an object of this invention to provide a means foreconomically and rapidly removing fins from iron castings.

It is-a further object of this invention to remove fins which arelocated in the casting so that their removal by mechanical means isdifficult or impractical.

This invention is predicated upon the fact that the rate of recationbetween an iron object and elemental chlorine is dependent upon twofactors. The first factor, of course, is the temperature obtainingwithin the system. The second factor is the thickness of the ironobject. The reaction between iron and elemental chlorine results in theproduction .of readily volatile ferric chloride. This reaction in commonwith most inorganic reactions is accelerated by increasing thetemperature. The sensitivity of the speed of this reaction to thethickness of the iron follows from the inability of thin iron todissipate the heat resulting from the initial reaction between the ironand the elemental chlorine. In thick iron this heat is dissipated intothe mass as fast as it is generated and the temperature of theiron-elemental chlorine interface cannot rise appreciably. In the caseof thin iron, the heat produced by the initial iron-elemental chlorinereaction serves to raise the temperature of the entire thin mass which,in turn, increases the rate of reaction between the elemental chlorineand the iron. This precipitates an exponential increase in the rate ofreaction between the elemental chlorine and the iron. Under suchcircumstances, thin iron masses quickly incandesce and disappear in theform of volatile ferric chloride. The interdependence between thethickness of the iron and the temperature at which an exponentialreaction can be initiated can be appreciated from the fact that steelwool Will incandesce in chlorine at a temperature less than the boilingpoint of water while iron as thick as thirty-thousandths of an inch willnot incandesce until a temperature of about 500 F. is employed. Thishigher temperature is probably fixed Patented Sept. 7, 1965 to someextent by the fact that it is just under the melting and boiling pointof ferric chloride.

In the execution of this invention it is contemplated that at least thefins of the casting be heated to a temperature to permit the initiationof this exponential reaction when exposed to elemental chlorine. In mostcases, and particularly in the case of internal fins, it is expedient toheat the entire casting to an appropriate temperature and then exposethe entire casting to elemental chlorine. Air should be removed ascompletely as possible from the system to avoid the production ofrelatively inert iron oxide and the deleterious presence of inertnitrogen. The elemental chlorine should be applied to the casting insuch a way that it does not physically cool the fins below the point atwhich the exponential reaction will take place. This may be accomplishedby simply immersing the casting in quiescent elemental chlorine. It isunnecessary to provide for circulation of the elemental chlorine if thesystem is free of air. The products of reaction of iron and elementalchlorine can only be ferrous chloride and ferric chloride. Ferricchloride is in itself highly corrosive to heated iron and ferrouschloride will react with elemental chlorine to produce ferric chloride.Consequently, no circulation of the elemental chlorine past the fins isnecessary. On the contrary, excessive movement of the elemental chlorinethrough the casting tends to blunt the difference in the action of theelemental chlorine upon the fins and the mass of the casting. Suchexcessive movement tends to accentuate the attack of the elementalchlorine upon the mass of the casting and to cool the fins below thepoint at which they will incandesce.

It is preferred to remove from the casting such as an internalcombustion engine cylinder head all of the sand both externally andinternally before treating with ele- -an enclosure and evacuate from theenclosure all possible air. The evacuated enclosure is then filled withelemental chlorine and the reaction allowed to proceed. It may beadvantageous to flush the container at least once with elementalchlorine followed by a second evacuation before admitting the elementalchlorine upon which reliance is placed for the cleaning.

In the case of external fins, it is unnecessary to heat the entirecasting. The cleaned casting may be placed in a refractory linedcontainer heated to a temperature sufliciently high to initiate thedesired exothermic reaction. This container is filled with chlorine andthe casting immersed in the chlorine. The minor bulk of the fins willcause them to preferentially heat to the temperatrue at which theexponential reaction will take place.

I claim as my invention: 1. The process of removing fins from a ferrousobject comprising exposing such object and fins to elemental chlorinewhile said fins are heated sufliciently to cause the object to theelemental chlorine when the fins have been substantially converted toferric chloride.

2. The process of removing fins from a ferrous casting comprislngexposing such casting and fins to elemental chlorine while such fins areheated sufficiently to cause them to react exothermically with theelemental chlorine at an exponentially increasing rate while maintainingthe remainder of the casting at a temperature at which suchexponentially increasing rate of reaction with elemental chlorine doesnot occur and terminating the exposure of the casting to elementalchlorine when the fins have been substantially converted to ferricchloride.

3. The process or removing fins from a ferrous casting comprisingexposing such castings and fins to elemental chlorine while such finsare heated at least to the boiling point of water to cause them to reactexothermically with the elemental chlorine at an exponentiallyincreasing rate while maintaining the remainder of the object at atemperature at which such exponentially increasing rate of reaction withelemental chlorine does not occur and terminating the exposure of thecasting to elemental chlorine when the fins have been substantiallyconverted to ferric chloride.

4. The process of removing internal fins from a ferrous castingcomprising heating said ferrous casting and fins to a temperature atleast as high as the boiling point of water, exposing the heated fins toelemental chlorine to cause them to react exothermically with theelemental chlori& at an exponentially increasing rate while theremainder of the casting reacts with the elemental chlorine at anessentially constant and much slower rate, and terminating the exposureof the casting to elemental chlorine when the fins have substantiallyall been converted to ferric chloride.

5. The process of removing internal fins from a ferrous castingcomprising heating said ferrous casting and fins to a temperaturebetween 500 and 800 F., exposing the heated fins to elemental chlorineto cause them to react exothermically with the elemental chlorine at anexponentially increasing rate while the remainder of the casting reactswith the elemental chlorine at an essentially constant and much slowerrate, and terminating the exposure of the casting to elemental chlorinewhen the fins have substantially been converted to ferric chloride.

6. The process of removing internal fins from a ferrous castingcomprising heating said ferrous casting and fins to a temperaturebetween 500 and 800 F., exposing the heated fins to elemental chlorineto cause them to react exothermically with the elemental chlorine at anexponentially increasing rate while the remainder of the casting reactswith the elemental chlorine at an essentially constant and much slowerrate, and terminating the exposure of the casting to the elementalchlorine when the fins have substantially been converted to ferricchloride, the temperature of the elemental chlorine and the relativemovement between the elemental chlorine and the fins being chosen sothat the physical cooling effect of the elemental chlorine does not coolthe fins below the point at which an exponentially increasing rate ofreaction is possible.

7. The method of removing internal fins from a ferrous castingcomprising heating said ferrous casting and fins to a temperaturebetween 500 and 800 F., immersing the casting and fins in essentiallyquiescent elemental chlorine to cause them to react exothermically withthe elemental chlorine at an exponentially increasing rate while theremainder of the casting reacts with the elemental chlorine at anessentially constant and much slower rate, and terminating the exposureof the casting to the elemental chlo- 4 rine when the fins have beensubstantially converted to ferric chloride.

8. The process of removing fins from a ferrous casting comprisingsupplying heat to the casting sufficiently rapidly to heat the fins butnot the mass of the casting to a temperature at lea-st as high as theboiling point of water, exposing the heated fins to elemental chlorineto cause the chlorine to react with the fins exothennically and at anexponentially increasing rate while the temperature of the mass of thecasting remains at a point when the reaction with the elemental chlorineis at a much slower and uniform rate, and terminating the exposure toelemental chlorine when the fins have been converted to ferric chloride.

9. The rocess of removing fins from a ferrous casting comprisingsupplying heat to the casting sufficiently rapidly to heat the fins atleast locally to a temperature of 500 to 800 F. while the mass of thecasting remains substantially cooler, exposing the heated fins toelemental chlorine to cause the elemental chlorine to react with thefins exothermically and at an exponentially increasing rate while thetemperature of the mass of the casting remains at a point where thereaction with the elemental chlorine is at a much slower and uniformrate, and terminating the exposure to elemental chlorine when the finshave been converted to ferric chloride.

10. The process for removing fins from a ferrous casting comprisingheating the casting to a temperature sufiiciently high to cause the finsto react exothermically and at an exponentially increasing rate withelemental chlorine, placing the casting in an enclosure, evacuating theair from the enclosure, adding elemental chlorine to the evactuatedenclosure and permitting the elemental chlorine and the fins to reactuntil the fins have been substantially converted to ferric chloride.

11. The process for removing fins from a ferrous casting comprisingheating the casting to a temperature sulficiently high to cause the finsto react exothermically and at an exponentially increasing rate withelemental chlorine, placing the casting in an enclosure, evacuating theair from the enclosure, adding elemental chlorine to the evacuatedenclosure, again evacuating the enclosure, adding elemental chlorineagain to the evacuated enclosure and permitting the elemental chlorineand the fins to react until the fins have been substantially convertedto ferric chloride.

References Cited by the Examiner UNITED STATES PATENTS 1,943,875 l/34Nagelvoort 148-16 X 2,083,692 6/37 Dorph et al 23-87 2,199,418 5/40Redmond et al. 134-19 X 2,288,980 7/42 Turin 134-19 2,389,838 11/45Bromberg 148-16 2,405,592 8/46 Manger et al 134-2 X 2,625,495 1/53 Coneet al 134-2 2,632,718 3/53 Brodell 134-30 X 2,679,466 5/54 Spendelow148-16 X OTHER REFERENCES Langmuir: Article in Journal American Chem.Soc., Vol. XXXVII, 1915, pages 1139-1l67.

MORRIS O. WOLK, Primary Examiner.

DONALL H. SYLVESTER, Examiner.

1. THE PROCESS OF REMOVING FINS FROM A FERROUS OBJECT COMPRISINGEXPOSING SUCH OBJECT ND FINS TO ELEMENTAL CHLORINE WHILE SAID FINS AREHEATED SUFFICIENTLY TO CAUSE THEM TO REACT EXOTHERMICALLY WITH THEELEMENTAL CHLORINE AT AN EXPONENTIALLY INCREASING RATE WHILE MAINTAININGTHE REMAINDER OF THE OBJECT AT A TEMPERATURE AT WHICH SUCH EXPONENTIALLYINCREASING RATE OF REACTION WITH ELEMENTAL CHLORINE DOES NOT OCCUR ANDTERMINATING THE EXPOSURE OF THE OBJECT TO THE ELEMENTAL CHLORINE WHENTHE FINS HAVE BEEN SUBSTANTIALLY CONVERTED TO FERRIC CHLORIDE.